PARP inhibitors in head and neck cancer: Molecular mechanisms, preclinical and clinical data

BRCA1 and BRCA2 as prognostic markers in oral squamous cell carcinoma: a minireview

Oral squamous cell carcinoma (OSCC), a subset of head and neck cancers, primarily originates in the epithelial tissues of the oral cavity. Despite advancements in treatment, the mortality rate for OSCC remains around 50%, underscoring the urgent need for improved prognostic markers. This review explores the role of the BRCA1 and BRCA2 genes-traditionally associated with breast and ovarian cancers-in the context of OSCC. We discuss the molecular pathways involving BRCA genes, their potential as diagnostics and prognostic biomarkers, and their implications for personalized treatment strategies, including addressing chemotherapy resistance. Furthermore, this review emphasizes the significance of genome stability in cancer progression and examines both current and emerging methodologies for detecting BRCA mutations in OSCC patients. Despite limited prevalence of BRCA mutations in OSCC compared to other cancers, their role in DNA repair and therapeutic response underscores their potential as clinical biomarkers. However, standardized, multicenter studies are still needed to validate their utility in OSCC management. A better understanding of the role of BRCA genes in OSCC could pave the way for more effective therapeutic approaches and improved patient outcomes.

Fluorinated chitosan mediated transepithelial delivery of sanguinarine-loaded platinum (IV) prodrug for intravesical instillation therapy of muscle-invasive bladder cancer

Cisplatin-based neoadjuvant chemotherapy is first-line strategy to inhibit progression and metastasis of muscle-invasive bladder cancer (MIBC). However, its clinical efficacy is often limited by drug resistance and severe systemic side effects, highlighting the urgent need for innovative therapeutic approaches. Despite advancements in cisplatin-based regimens, research on intravesical cisplatin delivery systems remains scarce. In this study, we developed an amphiphilic platinum(IV) prodrug micellar platform (Pt (IV)-DI-PEG) capable of efficiently encapsulating sanguinarine (San), which was further coated with fluorinated chitosan (FCS) to construct San@Pt(IV)-DI-PEG@FCS nanoparticles (SPFNPs) for intravesical instillation even targeting MIBC. The resulting SPFNPs demonstrated several advantages: the FCS coating facilitated enhanced trans-epithelial drug delivery by regulating bladder epithelial tight junction proteins, enabling efficient intravesical administration; Second, the glutathione (GSH)-responsive reduction of the Pt(IV) prodrug promoted tumor-targeted release of San and localized accumulation of Pt(II), while simultaneously depleting intracellular GSH. Furthermore, the released San induced reactive oxygen species (ROS) production, oxidative cleavage and inhibit the activation and function of poly (ADP-ribose) polymerase, collectively impairing nucleotide-excision repair and preventing the elimination of Pt-DNA adducts, resulting in persistent DNA damage, cell cycle arrest, and apoptosis in tumor cells. The synergistic effects of San and cisplatin were validated in both orthotopic mouse models and patient-derived orthotopic xenograft, demonstrating robust anti-tumor efficacy. This study underscores the potential of intravesical cisplatin formulations as a promising strategy for MIBC treatment, offering a shift from traditional systemic chemotherapy towards localized, targeted drug delivery systems.

Report of an Extremely Rare Case of BRCA-Positive Head and Neck Cancer: A New Disease on the Horizon?

Cancer of unknown primary (CUP) with metastatic squamous cell carcinoma (SCC) to the neck nodes is rare and represents <5% of all head and neck malignancies. The prognosis is poor; hence, there is a need for early comprehensive diagnostic evaluation and management. A BRCA mutation is rarely seen in patients with head and neck squamous cell carcinoma (HNSCC) with an incidence of only 5-10%. We hereby present a rare case report of CUP with metastatic neck nodes (SCC), unveiling a BRCA mutation on liquid biopsy. The patient responded very well with platinum-based cytotoxic chemotherapy followed by maintenance poly adenosine diphosphate ribose polymerase inhibitors (PARPi). This is a first-of-its-kind case in the head and neck region, especially in this part of the world, where tobacco-related head and neck cancer catches all the attention over human papillomavirus (HPV) positivity and other risk factors.

Alterations in the expression of homologous recombination repair (HRR) genes in breast cancer tissues considering germline BRCA1/2 mutation status

INTRODUCTION

Homologous recombination (HR) is a crucial DNA-repair mechanism, and its disruption can lead to the accumulation of mutations that initiate and promote cancer formation. The key HR genes, BRCA1 and BRCA2, are particularly significant as their germline pathogenic variants are associated with a hereditary predisposition to breast and/or ovarian cancer.

MATERIALS AND METHODS

The study was performed on 45 FFPE breast cancer tissues obtained from 24 and 21 patients, with and without the germline BRCA1/2 mutation, respectively. The expression of 11 genes: BRCA1, BRCA2, ATM, BARD1, FANCA, FANCB, FANCI, RAD50, RAD51D, BRIP1, and CHEK2 was assessed using Custom RT2 PCR Array (Qiagen), and results were analysed using R.

RESULTS

Cancer tissues from patients with BRCA1 or BRCA2 germline mutations displayed no significant differences in the expression of the selected HR genes compared to BRCA1 or BRCA2 wild-type cancer tissues. In BRCA1mut cancer tissues, BRCA1 expression was significantly higher than in BRCA2mut and BRCA wild-type cancer tissues.

CONCLUSIONS

In cancer tissues harbouring either BRCA1 or BRCA2 germline mutations, no significant differences in expression were observed at the mRNA level of any tested HR genes, except BRCA1. However, the significant differences observed in BRCA1 expression between germline BRCA1mut, germline BRCA2mut and BRCA1/2wt tissues may indicate a compensatory mechanism at the mRNA level to mitigate the loss of BRCA1 function in the cells.

Genome-wide characterization of the mutational landscape of proliferative verrucous leukoplakia

OBJECTIVES

Proliferative verrucous leukoplakia (PVL) is a rare but highly aggressive variant of oral leukoplakia that almost inevitably progresses to oral squamous cell carcinoma (OSCC). The aims of this study were to perform whole exome sequencing of a cohort of patients diagnosed with PVL and identify potential mutational profiles and pathways in this disorder.

STUDY DESIGN

A total of 12 oral cavity mucosal biopsies from 6 patients with oral lesions clinically compatible with PVL were used. Of these, 9 were diagnosed as dysplasia, 1 OSCC, and 2 hyperkeratosis/hyperplasia. Exome sequencing used the Ion AmpliSeq Exome platform. Ion Reporter software was used for variant calling, annotation, and filtering. Analysis and visualization of somatic mutations was carried out using the MAFtools R package.

RESULTS

Following exome sequencing and mutational profiling, we analyzed the profiles for cancer associated genes and signatures. Genes previously associated with OSCC, including HYDIN, MUC16, MAML3, CDKN2A, FAT1, and CASP8, were mutated in multiple samples. Several DNA damage repair genes including PARP1 were mutated in PVL samples. NOTCH and Hippo pathways were the most frequently impacted by mutation.

CONCLUSIONS

This genome wide characterization of premalignant PVL identifies both known and potentially novel oncogenic mechanisms in this disorder.

Triple Combinations of Histone Lysine Demethylase Inhibitors with PARP1 Inhibitor-Olaparib and Cisplatin Lead to Enhanced Cytotoxic Effects in Head and Neck Cancer Cells

PARP inhibitors are used to treat cancers with a deficient homologous recombination (HR) DNA repair pathway. Interestingly, recent studies revealed that HR repair could be pharmacologically impaired by the inhibition of histone lysine demethylases (KDM). Thus, we investigated whether KDM inhibitors could sensitize head and neck cancer cells, which are usually HR proficient, to PARP inhibition or cisplatin. Therefore, we explored the effects of double combinations of KDM4-6 inhibitors (ML324, CPI-455, GSK-J4, and JIB-04) with olaparib or cisplatin, or their triple combinations with both drugs, on the level of DNA damage and apoptosis. FaDu and SCC-040 cells were treated with individual compounds and their combinations, and cell viability, apoptosis, DNA damage, and gene expression were assessed using the resazurin assay, Annexin V staining, H2A.X activation, and qPCR, respectively. Combinations of KDM inhibitors with cisplatin enhanced cytotoxic effects, unlike combinations with olaparib. Triple combinations of KDM inhibitors with cisplatin and olaparib exhibited the best cytotoxic activity, which was associated with DNA damage accumulation and altered expression of genes associated with apoptosis induction and cell cycle arrest. In conclusion, triple combinations of KDM inhibitors (especially GSK-J4 and JIB-04) with cisplatin and olaparib represent a promising strategy for head and neck cancer treatment.

Overcoming Resistance to Standard-of-Care Therapies for Head and Neck Squamous Cell Carcinomas

Although there have been some advances during in recent decades, the treatment of head and neck squamous cell carcinoma (HNSCC) remains challenging. Resistance is a major issue for various treatments that are used, including both the conventional standards of care (radiotherapy and platinum-based chemotherapy) and the newer EGFR and checkpoint inhibitors. In fact, all the non-surgical treatments currently used for HNSCC are associated with intrinsic and/or acquired resistance. Herein, we explore the cellular mechanisms of resistance reported in HNSCC, including those related to epigenetic factors, DNA repair defects, and several signaling pathways. This article discusses these mechanisms and possible approaches that can be used to target different pathways to sensitize HNSCC to the existing treatments, obtain better responses to new agents, and ultimately improve the patient outcomes.

Therapeutic Advances and Challenges for the Management of HPV-Associated Oropharyngeal Cancer

The use of conventional chemotherapy in conjunction with targeted and immunotherapy drugs has emerged as an option to limit the severity of side effects in patients diagnosed with head and neck cancer (HNC), particularly oropharyngeal cancer (OPC). OPC prevalence has increased exponentially in the past 30 years due to the prevalence of human papillomavirus (HPV) infection. This study reports a comprehensive review of clinical trials registered in public databases and reported in the literature (PubMed/Medline, Scopus, and ISI web of science databases). Of the 55 clinical trials identified, the majority (83.3%) were conducted after 2015, of which 77.7% were performed in the United States alone. Eight drugs have been approved by the FDA for HNC, including both generic and commercial forms: bleomycin sulfate, cetuximab (Erbitux), docetaxel (Taxotere), hydroxyurea (Hydrea), pembrolizumab (Keytruda), loqtorzi (Toripalimab-tpzi), methotrexate sodium (Trexall), and nivolumab (Opdivo). The most common drugs to treat HPV-associated OPC under these clinical trials and implemented as well for HPV-negative HNC include cisplatin, nivolumab, cetuximab, paclitaxel, pembrolizumab, 5-fluorouracil, and docetaxel. Few studies have highlighted the necessity for new drugs specifically tailored to patients with HPV-associated OPC, where molecular mechanisms and clinical prognosis are distinct from HPV-negative tumors. In this context, we identified most mutated genes found in HPV-associated OPC that can represent potential targets for drug development. These include TP53, PIK3CA, PTEN, NOTCH1, RB1, FAT1, FBXW7, HRAS, KRAS, and CDKN2A.

KMT2 (MLL) family of methyltransferases in head and neck squamous cell carcinoma: A systematic review

BACKGROUND

The involvement of the KMT2 methyltransferase family in the pathogenesis of head and neck squamous cell carcinoma (HNSCC) remains elusive.

METHOD

This study adhered to the PRISMA guidelines, employing a search strategy in the LIVIVO, PubMed, Scopus, Embase, Web of Science, and Google Scholar databases. The methodological quality of the studies was assessed by the Joanna Briggs Institute.

RESULTS

A total of 33 studies involving 4294 individuals with HNSCC were included in this review. The most important alteration was the high mutational frequency in the KMT2C and KMT2D genes, with reported co-occurrence. The expression of the KMT2D gene exhibited considerable heterogeneity across the studies, while limited data was available for the remaining genes.

CONCLUSIONS

KMT2C and KMT2D genes seem to have tumor suppressor activities, with involvement of cell cycle inhibitors, regulating different pathways that can lead to tumor progression, disease aggressiveness, and DNA damage accumulation.

NAD+ Metabolism-Related Gene Profile Can Be a Relevant Source of Squamous Cell Carcinoma Biomarkers

Poor survival rates of squamous cell carcinomas (SCCs) are associated with high recurrence, metastasis, and late diagnosis, due in part to a limited number of reliable biomarkers. Thus, the identification of signatures improving the diagnosis of different SCC types is mandatory. Considering the relevant role of NAD+ metabolism in SCC chemoprevention and therapy, the study aimed at identifying new biomarkers based on NAD+ metabolism-related gene (NMRG) expression. Gene expression of 18 NMRGs and clinical-pathological information for patients with head and neck SCC (HNSCC), lung SCC (LuSCC), and cervix SCC (CeSCC) from The Cancer Genome Atlas (TCGA) were analyzed by several bioinformatic tools. We identified a 16-NMRG profile discriminating 3 SCCs from 3 non-correlated tumors. We found several genes for HNSCC, LuSCC, and CeSCC with high diagnostic power. Notably, three NMRGs were SCC-type specific biomarkers. Furthermore, specific signatures displayed high diagnostic power for several clinical-pathological characteristics. Analyzing tumor-infiltrating immune cell profiles and PD-1/PD-L1 levels, we found that NMRG expression was associated with suppressive immune microenvironment mainly in HNSCC. Finally, the evaluation of patient survival identified specific genes for HNSCC, LuSCC, and CeSCC with potential prognostic power. Therefore, our analyses indicate NAD+ metabolism as an important source of SCC biomarkers and potential therapeutic targets.

Phase I feasibility study of Olaparib in combination with loco-regional radiotherapy in head and neck squamous cell carcinoma

Purpose

PARP-inhibitors have potent radiosensitizing properties in pre-clinical models. To identify the maximum tolerated dose (MTD) of the PARP-inhibitor Olaparib in combination with radiotherapy in patients with head and neck cancer, a single institutional phase-I dose escalation trial was initiated.

Patients and methods

The starting dose of Olaparib was 25 mg BID, combined with radiotherapy (70 Gy in 35 fractions). The MTD was defined as the highest dose-level at which not more than 20 % of patients experience dose-limiting toxicities (DLT) or as the highest reached dose in the absence of DLT's.

Results

One week Olaparib-only treatment (25 mg QD) was administered to all patients prior to the start of radiotherapy. In dose-level I, Olaparib (25 mg BID) was combined with accelerated radiotherapy (70 Gy in 6 weeks). Because of DLT's in 3 of the 4 treated patients (acute tracheotomy 5 and 7 months and osteoradionecrosis 7 months after treatment), the Olaparib dose was de-escalated to 25 mg QD, and combined with conventional radiotherapy (70 Gy in 7 weeks) (dose-level II). There were no DLT's observed in 5 patients treated within dose-level II. After a median follow-up of 60 months, the 4-year LRC and OS rates were 77.8 % and 88.9 %, respectively.

Conclusion

Olaparib 25 mg QD combined with conventionally fractionated radiotherapy was well tolerated and identified as the MTD while severe DLT's were observed when Olaparib 25 mg BID was combined with accelerated radiation. This combination might be further explored in future Olaparib dose escalation studies in patients with locally-advanced HNSCC unfit for cisplatin-based chemoradiotherapy.

Revisiting the concept of neoadjuvant and induction therapy in head and neck cancer with the advent of immunotherapy

The treatment of locally advanced (LA) Head and Neck Squamous Cell Carcinoma (HNSCC) is based on surgery followed by (chemo)radiation or on curative (chemo)radiation, depending on site and stage. Despite optimal locoregional treatment, about 50% of patients recur, with a huge impact on prognosis and substantial morbidity. The advent of immunotherapy (IT) with immune checkpoint inhibitors (ICIs) changed the paradigm of systemic treatment for recurrent/metastatic (RM) disease, showing activity, efficacy, and safety in both platinum-resistant and platinum-naïve patients. Such data led clinicians to design clinical trials to investigate early administration of IT even in the neoadjuvant or window of opportunity setting. In this review, we examine the published and ongoing trials investigating IT in the neoadjuvant setting for LA HNSCC. We address the current challenges of this treatment modality: optimal patient selection for neoadjuvant IT; choosing the appropriate systemic approach to enhance response without compromising tolerability; determining the ideal study endpoint, with a focus on major pathological response as a potential surrogate for overall survival; evaluating treatment response through imaging, considering the discordance between radiological and pathological assessments; and the influence of neoadjuvant IT response on locoregional treatment de-escalation strategies.

Taxanes in the Treatment of Head and Neck Squamous Cell Carcinoma

Taxanes, particularly docetaxel (DTX), has been widely used for combination therapy of head and neck squamous cell carcinoma (HNSCC). For locally advanced unresectable HNSCC, DTX combined with cisplatin and 5-fluorouracil as a revolutionary treatment revealed an advantage in the improvement of patient outcome. In addition, DTX plus immune check inhibitors (ICIs) showed low toxicity and an increased response of patients with recurrent or metastatic HNSCC (R/M HNSCC). Accumulated data indicate that taxanes not only function as antimitotics but also impair diverse oncogenic signalings, including angiogenesis, inflammatory response, ROS production, and apoptosis induction. However, despite an initial response, the development of resistance remains a major obstacle to treatment response. Taxane resistance could result from intrinsic mechanisms, such as enhanced DNA/RNA damage repair, increased drug efflux, and apoptosis inhibition, and extrinsic effects, such as angiogenesis and interactions between tumor cells and immune cells. This review provides an overview of taxanes therapy applied in different stages of HNSCC and describe the mechanisms of taxane resistance in HNSCC. Through a detailed understanding, the mechanisms of resistance may help in developing the potential therapeutic methods and the effective combination strategies to overcome drug resistance.

Phase II Window Study of Olaparib Alone or with Cisplatin or Durvalumab in Operable Head and Neck Cancer

Purpose

We conducted a phase II randomized noncomparative window of opportunity (WOO) trial to evaluate the inhibition of cellular proliferation and the modulation of immune microenvironment after treatment with olaparib alone or in combination with cisplatin or durvalumab in patients with operable head and neck squamous cell carcinoma (HNSCC).

Experimental Design

Forty-one patients with HNSCC were randomized to cisplatin plus olaparib (arm A), olaparib alone (arm B), no treatment (arm C) or durvalumab plus olaparib (arm D). The primary endpoint was to evaluate the percentage of patients in each arm that achieved a reduction of at least 25% in Ki67. Secondary endpoints included objective response rate (ORR), safety, and pathologic complete response (pCR) rate. Paired baseline and resection tumor biopsies and blood samples were evaluated for prespecified biomarkers.

Results

A decrease in Ki67 of at least 25% was observed in 44.8% of treated patients, as measured by quantitative immunofluorescence. The ORR among treated patients was 12.1%. pCR was observed in 2 patients. Two serious adverse events occurred in 2 patients.Programmed death ligand 1 (PD-L1) levels [combined positive score (CPS)] were significantly higher after treatment in arms A and D. Expression of CD163 and colony-stimulating factor 1 receptor (CSF1R) genes, markers of M2 macrophages, increased significantly posttreatment whereas the expression of CD80, a marker of M1 macrophages, decreased.

Conclusion

Preoperative olaparib with cisplatin or alone or with durvalumab was safe in the preoperative setting and led to decrease in Ki67 of at least 25% in 44.8% of treated patients. Olaparib-based treatment modulates the tumor microenvironment leading to upregulation of PD-L1 and induction of protumor features of macrophages.

Significance

HNSCC is characterized by defective DNA repair pathways and immunosuppressive tumor microenvironment. PARP inhibitors, which promote DNA damage and "reset" the inflammatory tumor microenvironment, can establish an effective antitumor response. This phase II WOO trial in HNSCC demonstrated the immunomodulatory effects of PARP inhibitor-induced DNA damage. In this chemo-naïve population, PARP inhibitor-based treatment, reduced tumor cell proliferation and modulated tumor microenvironment. After olaparib upregulation of PD-L1 and macrophages, suggests that combinatorial treatment might be beneficial.

Synopsis

Our WOO study demonstrates that preoperative olaparib results in a reduction in Ki67, upregulation of PD-L1 CPS, and induction of protumor features of macrophages in HNSCC.

Enhancing the anti-tumor response by combining DNA damage repair inhibitors in the treatment of solid tumors

The anti-cancer efficacy of anti-malignancy therapies is related to DNA damage. However, DNA damage-response mechanisms can repair DNA damage, failing anti-tumor therapy. The resistance to chemotherapy, radiotherapy, and immunotherapy remains a clinical challenge. Thus, new strategies to overcome these therapeutic resistance mechanisms are needed. DNA damage repair inhibitors (DDRis) continue to be investigated, with polyadenosine diphosphate ribose polymerase inhibitors being the most studied inhibitors. Evidence of their clinical benefits and therapeutic potential in preclinical studies is growing. In addition to their potential as a monotherapy, DDRis may play an important synergistic role with other anti-cancer therapies or in reversing acquired treatment resistance. Here we review the impact of DDRis on solid tumors and the potential value of combinations of different treatment modalities with DDRis for solid tumors.

Partial response to niraparib in combination with tislelizumab in a patient with metastatic undifferentiated tonsillar carcinoma: a case report and literature review

Undifferentiated tonsillar carcinoma is an extremely rare head and neck cancer. The treatment options are challenging due to insensitivity to chemotherapy and easy development of drug resistance. In this study, we reported a case of advanced undifferentiated tonsillar carcinoma with multiple mediastinal lymph node metastases that failed to respond to chemotherapy. Next-generation sequencing (NGS) revealed germline BReast CAncer gene (BRCA) 1 mutation and a high tumor mutational burden. Poly (adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors have demonstrated efficacy in solid tumors with BRCA1/2 mutations. Immune checkpoint inhibitors (ICIs) provide a treatment option for unresectable head and neck cancer. After local control treatment by embolization, niraparib and tislelizumab were administered to this patient. A partial response (PR) was achieved, and progression-free survival (PFS) and overall survival (OS) were 12 months and 19 months, respectively. This case reveals molecular profiling as an important therapeutic strategy for rare malignancies with no standard of care. Moreover, the underlying synergistic antitumor activity of PARPi and PD-L1 blockade was reviewed.

Targeted Therapy with PI3K, PARP, and WEE1 Inhibitors and Radiotherapy in HPV Positive and Negative Tonsillar Squamous Cell Carcinoma Cell Lines Reveals Synergy while Effects with APR-246 Are Limited

Human papillomavirus positive (HPV⁺) tonsillar and base of tongue cancer (TSCC/BOTSCC) is rising in incidence, but chemoradiotherapy is not curative for all. Therefore, targeted therapy with PI3K (BYL719), PARP (BMN-673), and WEE1 (MK-1775) inhibitors alone or combined was pursued with or without 10 Gy and their effects were analyzed by viability, proliferation, and cytotoxicity assays on the TSCC/BOTSCC cell lines HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A. Effective single drug/10 Gy combinations were validated on additional TSCC lines. Finally, APR-246 was assessed on several TSCC/BOTSCC cell lines. BYL719, BMN-673, and MK-1775 treatments induced dose dependent responses in HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A and when combined with 10 Gy, synergistic effects were disclosed, as was also the case upon validation. Using BYL719/BMN-673, BYL719/MK-1775, or BMN-673/MK-1775 combinations on HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A also induced synergy compared to single drug administrations, but adding 10 Gy to these synergistic drug combinations had no further major effects. Low APR-246 concentrations had limited usefulness. To conclude, synergistic effects were disclosed when complementing single BYL719 BMN-673 and MK-1775 administrations with 10 Gy or when combining the inhibitors, while adding 10 Gy to the latter did not further enhance their already additive/synergistic effects. APR-246 was suboptimal in the present context.

Targeting DNA damage response as a potential therapeutic strategy for head and neck squamous cell carcinoma

Cells experience both endogenous and exogenous DNA damage daily. To maintain genome integrity and suppress tumorigenesis, individuals have evolutionarily acquired a series of repair functions, termed DNA damage response (DDR), to repair DNA damage and ensure the accurate transmission of genetic information. Defects in DNA damage repair pathways may lead to various diseases, including tumors. Accumulating evidence suggests that alterations in DDR-related genes, such as somatic or germline mutations, single nucleotide polymorphisms (SNPs), and promoter methylation, are closely related to the occurrence, development, and treatment of head and neck squamous cell carcinoma (HNSCC). Despite recent advances in surgery combined with radiotherapy, chemotherapy, or immunotherapy, there has been no substantial improvement in the survival rate of patients with HNSCC. Therefore, targeting DNA repair pathways may be a promising treatment for HNSCC. In this review, we summarized the sources of DNA damage and DNA damage repair pathways. Further, the role of DNA damage repair pathways in the development of HNSCC and the application of small molecule inhibitors targeting these pathways in the treatment of HNSCC were focused.

Why responses to immune checkpoint inhibitors are heterogeneous in head and neck cancers: Contributions from tumor-intrinsic and host-intrinsic factors

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment including in head and neck squamous cell carcinomas (HNSCCs); however, only a fraction of HNSCC patients respond to ICI, whereas the majority fail to do so. The mechanisms underlying such variable responses remain incompletely understood. A better understanding of such mechanisms may broaden the spectrum of responding patients and enhance the rate of ICI response. HNSCCs exhibit a high level of genetic heterogeneity, manifested as mutations or amplifications of oncogenes (e.g., PIK3CA) and mutations of tumor suppressor genes (e.g., TP53). The immune tumor microenvironment (TME) of HNSCCs also varies significantly in composition and in relative abundance of distinct immune subsets such as CD8 tumor-infiltrating lymphocytes (TILs) or tumor-associated macrophages (TAMs), which represents a high degree of immunological heterogeneity. Here, we briefly discuss how heterogeneous ICI responses may be attributed to tumor-intrinsic factors, including genetic, transcriptional, and functional variations in tumor cells, and host-intrinsic factors, including cellular composition of the TME (e.g., CD8 TILs and TAMs), and host-intrinsic differences in the T cell receptor (TCR) repertoire of CD8 TILs. We also discuss the potential impact of these factors on designing strategies for personalized immunotherapy of HNSCCs.

Checkpoint Inhibitors in Cancer Therapy: Clinical Benefits for Head and Neck Cancers

Recently, considerable progress has been achieved in cancer immunotherapy. Targeted immune checkpoint therapies have been established for several forms of cancers, which resulted in a tremendous positive impact on patient survival, even in more advanced tumor stages. With a better understanding of cellular responses to immune checkpoint therapies, it will soon be feasible to find targeted compounds which will make personalized medicine practicable. This is a great opportunity, but it also sets tremendous challenges on both the scientific and clinical aspects. Head and neck tumors evade immune surveillance through various mechanisms. They contain fewer lymphocytes (natural killer cells) than normal tissue with an accumulation of immunosuppressive regulatory T cells. Standard therapies for HNSCC, such as surgery, radiation, and chemotherapy, are becoming more advantageous by targeting immune checkpoints and employing combination therapies. The purpose of this review is to provide an overview of the expanded therapeutic options, particularly the combination of immune checkpoint inhibition with various conventional and novel therapeutics for head and neck tumor patients.

The role of DNA damage repair (DDR) system in response to immune checkpoint inhibitor (ICI) therapy

As our understanding of the mechanisms of cancer treatment has increased, a growing number of studies demonstrate pathways through which DNA damage repair (DDR) affects the immune system. At the same time, the varied response of patients to immune checkpoint blockade (ICB) therapy has prompted the discovery of various predictive biomarkers and the study of combination therapy. Here, our investigation explores the interactions involved in combination therapy, accompanied by a review that summarizes currently identified and promising predictors of response to immune checkpoint inhibitors (ICIs) that are useful for classifying oncology patients. In addition, this work, which discusses immunogenicity and several components of the tumor immune microenvironment, serves to illustrate the mechanism by which higher response rates and improved efficacy of DDR inhibitors (DDRi) in combination with ICIs are achieved.

Mitotic Checkpoints and the Role of WEE1 Inhibition in Head and Neck Squamous Cell Carcinoma

ABSTRACT

The WEE1 kinase family plays a crucial role in cell cycle regulation and DNA damage response pathways in malignant cells. Inhibition of WEE1 effectively overrides G2 cell cycle arrest and results in the accumulation of extensive DNA damage within dividing cells, potentiating mitotic catastrophe and cell death. As such, the development of WEE1 inhibitors as antineoplastic therapeutics has gained increasing interest in recent years. In particular, the role of WEE1 inhibitors for treatment of head and neck squamous cell carcinomas remains an area of active research with both preclinical and clinical studies investigating their use as both single-agent therapy and chemosensitizers when used in tandem with traditional chemotherapy, particularly in the context of TP53-mutant tumors. Here, we review the relevant available preclinical and clinical data on hand investigating the efficacy of WEE1 inhibitors for the treatment of head and neck cancers.

PARP1 Upregulation in Recurrent Oral Cancer and Treatment Resistance

First-line treatments for oral cancer typically include surgery, radiation, and in some cases, chemotherapy. Radiation and oral cancer chemotherapeutics confer cytotoxicity largely by inducing DNA damage, underscoring the importance of the cellular DNA damage repair and response pathways in cancer therapy. However, tumor recurrence and acquired resistance, following the initial response to treatment, remains as a major clinical challenge. By analyzing oral tumor cells derived from the primary and recurrent tumors of the same patient, our study revealed upregulated PARP1 expression in the recurrent tumor cells. Cisplatin and 5-fluorouracil treatment further augmented PARP1 expression in the recurrent, but not the primary, tumor cells. Post-treatment upregulation of PARP1 was dependent on the catalytic activities of PARP and CDK7. Consistent with the established function of PARP1 in DNA repair, we showed that overexpression of PARP1 rendered the primary tumor cells highly resistant to DNA damage treatment. Conversely, PARP inhibition partially reversed the treatment resistance in the recurrent tumor cells; combinatorial treatment using a PARP inhibitor and cisplatin/5-fluorouracil significantly sensitized the tumor response in vivo. Taken together, we reported here PARP1 upregulation as a clinically relevant mechanism involved in oral cancer recurrence, and suggested the clinical benefit of PARP inhibitors, currently approved for the treatment of several other types of cancer, in oral cancer.

The Key Differences between Human Papillomavirus-Positive and -Negative Head and Neck Cancers: Biological and Clinical Implications

Head and neck squamous cell carcinoma (HNSCC) is a unique malignancy associated with two distinct risk factors: exposure to typical carcinogens and infection of human papillomavirus (HPV). HPV encodes the potent oncoproteins E6 and E7, which bypass many important oncogenic processes and result in cancer development. In contrast, HPV-negative HNSCC is developed through multiple mutations in diverse oncogenic driver genes. While the risk factors associated with HPV-positive and HPV-negative HNSCCs are discrete, HNSCC patients still show highly complex molecular signatures, immune infiltrations, and treatment responses even within the same anatomical subtypes. Here, we summarize the current understanding of biological mechanisms, treatment approaches, and clinical outcomes in comparison between HPV-positive and -negative HNSCCs.

Targeting DNA Damage Response and Repair to Enhance Therapeutic Index in Cisplatin-Based Cancer Treatment

Platinum-based chemotherapies, such as cisplatin, play a large role in cancer treatment. The development of resistance and treatment toxicity creates substantial barriers to disease control, yet. To enhance the therapeutic index of cisplatin-based chemotherapy, it is imperative to circumvent resistance and toxicity while optimizing tumor sensitization. One of the primary mechanisms by which cancer cells develop resistance to cisplatin is through upregulation of DNA repair pathways. In this review, we discuss the DNA damage response in the context of cisplatin-induced DNA damage. We describe the proteins involved in the pathways and their roles in resistance development. Common biomarkers for cisplatin resistance and their utilization to improve patient risk stratification and treatment personalization are addressed. Finally, we discuss some of the current treatments and future strategies to circumvent the development of cisplatin resistance.

The Prognostic Value of the DNA Repair Gene Signature in Head and Neck Squamous Cell Carcinoma

Purpose

To construct a prognostic signature composed of DNA repair genes to effectively predict the prognosis of patients with head and neck squamous cell carcinoma (HNSCC).

Methods

After downloading the transcriptome and clinical data of HNSCC from the Cancer Genome Atlas (TCGA), 499 patients with HNSCC were equally divided into training and testing sets. In the training set, 13 DNA repair genes were screened using univariate proportional hazard (Cox) regression analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis to construct a risk model, which was validated in the testing set.

Results

In the training and testing sets, there were significant differences in the clinical outcomes of patients in the high- and low-risk groups showed by Kaplan-Meier survival curves (P < 0.001). Univariate and multivariate Cox regression analyses showed that the risk score had independent prognostic predictive ability (P < 0.001). At the same time, the immune cell infiltration, immune score, immune-related gene expression, and tumor mutation burden (TMB) of patients with HNSCC were also different between the high- and low-risk groups (P < 0.05). Finally, we screened several chemotherapeutics for HNSCC, which showed significant differences in drug sensitivity between the high- and low-risk groups (P < 0.05).

Conclusion

This study constructed a 13-DNA-repair-gene signature for the prognosis of HNSCC, which could accurately and independently predict the clinical outcome of the patient. We then revealed the immune landscape, TMB, and sensitivity to chemotherapy drugs in different risk groups, which might be used to guide clinical treatment decisions.